A novel fibre optic acoustic emission sensor

This paper presents the design, theory, characterisation and application of a novel fibre optic acoustic emission (AE) sensor. The sensor consists of a pair of optical fibres that are heated, fused and drawn to create a fused-tapered region that is sensitive to acoustic perturbations. The sensor is housed in a silica V-groove. The modelling of this fibre optic AE sensor is presented with a finite element analysis on the strain field based on the effect of the geometry within the sensing region. The characterisation of the sensor was carried out using a glass block with 160mm thickness as an acoustic medium. The applications of this sensor were demonstrated in three experiments. Firstly, the sensor was surface-mounted in carbon fibre reinforced composite samples and tested to failure under tensile loading. In the second experiment, the sensor was surface-mounted on double-cantilever Mode-I test specimens. The AE response from the sensor was correlated to the inferred modes of failure during the Mode-I test. In the third experiment, the sensor was surface-mounted onto the composite "blow-off" test samples. The feasibility of using the sensor to detect damage development in real-time was demonstrated.